1. Field of the Invention
This invention relates to door closure mechanisms, for example torque rod torsion mechanisms for swing doors.
2. Related Art
Door closure mechanisms are common features for automatically closing a door and/or insuring an adequate seal between the door and the surrounding door frame. For example, swing doors often include automatic closure mechanisms to return the door to its original closed position after the door is released. For such doors as commercial refrigerator doors, used in supermarkets, convenience stores and the like, door closure mechanisms are used to return the door to the closed position after a customer has viewed and/or selected product from the case. After the customer releases the door, the closure mechanism moves or biases the door to its original positioned in the surrounding door frame. Typically, a magnetic gasket strip and magnetic plate form a seal between the door and the surrounding frame. The closure mechanism contributes to insuring an appropriate seal between the door and the surrounding frame.
Commercial refrigerator doors typically use a torsion or torque rod mechanism for closing the swing doors. The torque rod mechanism is an assembly of a spring steel or other torsion rod and a base that one end of the torsion rod is attached to. The base serves as a reference point stationary relative to the surrounding frame for the torsion rod, so that opening of the door applies torque to the torque rod. The base also properly positions the torque rod assembly in a vertical door frame element end may also serve as a lower door hinge pin. The second end of the torque rod is anchored to the door so that opening the door will twist the torque rod between the second end and the base supported by the surrounding frame. Anchoring the second end in the door may be accomplished by bending the second end at a 90 degree angle relative to the remainder of the torque rod. The bent second end may be placed in a holding block and inserted into a hollow portion of a vertical door frame element of a vertical swing door. One type of door closure mechanism for swing doors is shown and described in U.S. Pat. No. 4,696,078 by Stromquist, issued Sept. 29, 1987, entitled xe2x80x9cCombined Adjustable Door Hinge Pin Socket And Adjustable Torque Rod Anchor Devicexe2x80x9d, incorporated herein by reference.
The base and torque rod are typically separate parts joined together to form an assembly where the torque rod is fixed to the base. In one configuration, the base is a molded or die cast aluminum part having a square opening extending straight through the center for accepting the square first end of the spring steel torque rod. Sufficient clearance is provided between the inside surface of the base and the external mating surface of the torque rod to permit insertion of the torque rod in the base with sufficient ease to minimize the time required for assembly of the base and torque rod. One surface of the base is then peened on opposite sides of the torque rod to push adjacent portions of the base against the corresponding surfaces of the torque rod.
Occasionally, the base may crack or break in such a way that the torque rod is no longer securely fixed in the base. Consequently, the bias provided by the torque rod is lost. It is possible that stresses are developed in the molded aluminum base as a result of the torsion developed in the torque rod, which may be aggravated by impurities in the base or by stresses, such as by excessive peening.
A door closure mechanism is described which provides a more reliable assembly and which is more easily manufactured. It also reduces the possibility of failure of the door closure mechanism. In one preferred embodiment, the door closure mechanism includes a base and then opening in the base defined by surfaces which converge toward each other. A resilient element such as a torque rod engages and mates with the opening in such a way as to fix the torque rod in the base. Preferably, the torque rod has a square cross-section and the opening in the base is a square opening, and the opening includes a draft so that the engagement between the torque rod and the opening becomes tighter as the torque rod extends further into the base.
In further preferred embodiment so the invention, the opening in the base is defined by four walls oriented at right angles with respect to each other, and the torque rod has a square cross-section. As in conventional torque rods, the torque rod is made of spring steel. The four walls of the base extend from one surface of the base longitudinally parallel to an axis of the base to a corresponding set of inwardly angled walls, which may be formed as chamfered surfaces. The chamfered surfaces may be formed as a draft in the opening. The chamfered surfaces serve to partially neck down the inserted end of the torque rod, thereby fully seating the torque rod in the base.
These and other features of the invention will be more fully understood after considering the drawings, a brief description of which is set forth below, and the following detailed description of the preferred embodiments.